Refrigerant charging/recovery equipment heretofore have used a flexible hose to provide for connection to a refrigeration system being serviced, such as an automobile air conditioning system, to enable the refrigerant to be charged into or sucked out of the system. The flexible hose has been provided with a fitting at its free end for coupling to a service fitting provided in the refrigeration system. The service fitting usually is equipped with a check valve to prevent the escape of refrigerant from the refrigeration system when the flexible hose is not coupled thereto. A commonly employed check valve has been the inexpensive Schrader-type valve.
Because the service fitting often is in a difficult to reach position and/or at an awkward orientation, the refrigerant conveying hose of the charging/recovery equipment should be easy to flex to facilitate alignment of the fitting at the end of the hose with the service fitting of the refrigeration system. For this reason, prior art refrigerant conveying hoses have been made largely from rubber materials, a typical hose having a three-layered structure consisting of an inner rubber layer or core, an intermediate layer of braided synthetic fiber reinforcement, and an outer or cover layer of rubber.
These prior art rubber hoses were quite acceptable when there was less concern about the escape of refrigerants to the atmosphere. In the past, the refrigerant left in the refrigerant conveying hose after disconnection from the service fitting was allowed to escape to the atmosphere. However, today this is undesirable and any loss of refrigerants, such as Freon, to the atmosphere is considered by many to be undesirable. For this reason, it is known to put a manually operated shut-off valve at the end of the refrigerant conveying hose to prevent the escape of refrigerant from the hose when disconnected from the service fitting.
When the refrigerant is trapped in the conveying hose, a problem arises from the use of the above mentioned prior art rubber hoses. These hoses suffer from the problem of progressive escape of the refrigerant contained therein because of rubber's comparatively high gas permeability. Hence, refrigerant trapped in the refrigerant conveying line, which may be of considerable length, will permeate out through the walls of the hose and escape to the atmosphere.
In order to overcome this problem, there has been provided a hose including a non-permeating nylon core tube, an intermediate braided synthetic fiber reinforcement layer and an outer thermoplastic or rubber cover layer. Although exhibiting improved resistance to refrigerant permeation, this is at the expense of comparatively higher rigidity, i.e., reduced flexibility.
Also known and described in U.S. Pat. No. 5,089,074 is a flexible hose construction comprising an inner corrugated hose made of polymeric material, an outer sleeve of reinforcing material disposed in telescoping relation on the inner hose, an outer cover layer, and a tube of polymeric material disposed between the sleeve of reinforcing material and the inner hose and extending in a generally straight-line manner from apex to apex of the hose corrugations so as to tend to prevent the sleeve of reinforcing material from entering into the recesses of the inner hose by an amount that would substantially reduce the flexibility characteristics of the inner hose. The inner corrugated hose, intermediate tube and outer cover layer are all said to be made of a suitable polymeric material and, more specifically, to be made of a thermoplastic material. Consequently, such hose construction is perceived as still having considerable stiffness when compared to rubber hoses previously used in refrigerant charging/recovering equipment.
Accordingly, a need exists, especially for use in refrigerant charging/recovery equipment, for a refrigerant conveying hose having low permeability associated with hoses that use an inner nylon core and high flexibility associated with rubber hoses.